Brake



w. J. RYAN Nov. 26, 1940.

BRAKE Filed Jan. 26, 1938 V [I14 will 'IIIIIIII WILL/FM .J. EymvPatented Nov. 26, 1940 BRAKE William J. Ryan, Davenport, Iowa, assignorto Ralph J. Burton, Detroit, Mich.

Application January 26, 1938, Serial No. 186,920

4 Claims.

and claimed several automatic adjusters applied to brakes of this andother types, and the present invention relates to improvements thereon.

Many attempts to provide automatic brake adjusters have been made, andthe majority of these utilized the excessive movement of the brakingelements resulting from wear to determine the need for adjustment and tocause it to take place. However, it was discovered that excessivemovement of the braking elements also occurred from other causes thanwear. For example, it is now well known that severe use of the brakesliberates a large amount of heat and thereby causes an appreciableexpansion of the brake drum or corresponding element. The expansion ofthe drum naturally requires that the braking elements move farther inorder to contact it. In adjusters utilizing the above principle, theexpansion of the drum would cause adjustment to take place,'and thesubsequent cooling and contraction of the drum would then take up thenormal clearance and lock the brake.

I have developed a new principle of brake adjustment wherein I measurethe actual wear of the braking elements and compensate therefor, andseveral mechanisms employing this new principle have been shown in myabove-identified application.

Consequently an object of my invention is to provide for two-shoe,shiftable anchorage, servo brakes an improved automatic adjusterutilizing the wear principle.

Another object is to provide a two-shoe shiftable-anchorage servo brakewhich is continuously, positively and accurately adjusted by automaticmeans in accordance with the actual wear of the brake shoe lining.

I prefer to accomplish these objects by providing that, in theirreleased position, one adjacent pair of the shoe ends are held inengagement with the anchorage means by return springs, and by providingintermediate the ends of each of the shoes a return stop which isrepositioned by engagement with the drum as the shoe wears, and byproviding between the other adjacent pair of shoe ends, a floatingarticulatmg thrust element which is freely expansible to permit theshoes to separate as they are repositioned by said return stops, butwhich is not compressible so as to transmit thrust between the shoeswhen the brake is applied. The above and other objects and desirableparticular constructions will more fully appear upon reference to thefollowing detailed description of two embodiments of my inventionillustrated in the accompanying drawing, in which: 10

Figure 1 is a section just inside the head of the drum of a brakeembodying my invention;

Figure 2 is a section on the line 2-2 of Figure 1; and

Figure 3 is a fragmentary view corresponding 1 to a portion of Figure 1of a modification.

InFigure 1 there is shown a brake comprising a rotatable drum ID, afixed backing plate I2 1 closing the open end of the drum, and a pair ofgenerally semi-circular shoes I4 and it within 20 the drum. The shoesare formed with webs l8, rims 20 and friction linings 22 adapted tofrica tionally engage the inner surface of the drum l0.

Between one pair of adjacent shoe ends is an anchor pin 24 adapted to beengaged by com- 2 plementary notches formed in the ends of the webs l8of the shoes I4 and i6. Return springs 26 and 28 serve to return andhold the shoe ends against the anchor pin 24.

Radially inwardly of said anchor pin is a 30 brake applying motor 30comprising a hydraulic cylinder 32, pistons 34 and 36 and piston rods 38and 40 respectively engaging the shoes 54 and it to spread them intoengagement with the drum Ill. 35

Between the other pair of adjacent shoe ends is a; floatingtarticulating thrust. member 42 comprising a socket member 44non-rotatably engaging the web of shoe l4, a screw member 46 having oneend threaded into said socket 40 and its other end rotatably received ina second socket member 48 non-rotatably engaging the web of the shoe 16.The screw member 46 has a flange .50 intermediate its length, and ahelical torsion spring 52 is positioned between this flange and the endof the, socket member 44 and torsionally engages said flange and socketmember so as to tend to rotate the screw member 46 in a direction toscrew it out of the 50 socket and thereby elongate the entire thrustmember 42. Tensionezi between the said other pair of shoe ends is aspring 54 acting to hold the shoes and member 42, together, and exertinga pressure on the member 42 suflicient to 55 prevent its elongationunder the force of the spring 62. v

Between the ends of each of the shoes I4 and I6 andadiacent therespective webs I8 are stop pins 68 and 68 secured to the backing plateby means of nuts 62 and eccentrically positioned threaded projections 68formed with screw driver slots (see Fig.2).

In contact with these stops, when the brake is released, are stopengaging plungers 64 and 66 of rectangular cross section slidablysecured to the webs of the respective shoes I4 and. I6 by means ofhousings 68 and I8 welded or otherwise secured to said webs. Each ofthese plungers projects through an opening 12 or 14 formed in therespective rims 26 and linings 22 of the shoes and terminates flush withthe surface of the lining.

The housings 68 and I8 are provided with recesses 16 and I8 each ofwhich has a surface 88 disposed at an angle to the edge of the plungersand, contacting these surfaces and the plungers, are rollers 82 urgedinto locking engagement with the plunger by means of springs 84. It willbe noted that the surfaces are inclined in a direction so that outwardmovement of the plungers is prevented by the rollem 82 while inwardmovement is freely permitted.

The usual' steady rests 86 are provided on each shoe to hold itresiliently against the backing plate.

The arrow A (Fig. 1) shows the normal forward direction of rotation ofthe brake drum. In order to prevent anchor click when the brake isapplied in the forward direction it is usual to make the spring 28stronger than the spring 26 whereby shoe I4 will move into engagementwith the drum while shoe I6 remains in contact with the anchor.

When the brake is initially assembled, plungers 64 and 66 are positionedflush with the linings 22 of the respective shoes I4 and I6, and theeccentric stop pins 56 and 58 are rotated until they contact theplungers 64 or 66 and move the shoes toward the drum to obtain a desirednormal clearance between the shoes and the drum.

The spring 54 is lighter than the springs 26 or 28 so the shoes pivotabout the anchor pin 24, and the ends opposite the anchor spread apartstretching spring 54 and permitting the torsion spring 52 to rotate thescrew member 46. This expands the thrust member 42 until it occupies thefull space between the shoe ends.

Thereafter the brake is operated in the usual manner. For example, withthe drum rotating in the forward direction, hydraulic pressure appliedto the motor 30 forces the shoe I4 against the drum. The braking forceof the shoe I4 is applied through the thrust member 42 to the shoe I6,and the braking force of the shoe I6 is in turn applied to the anchorpin 24.

The same thing occurs in reverse braking except that when the shoe I4engages the drum, the friction carries the shoes around in a clockwisedirection (Fig. 1) until the shoe I4 engages the anchorpin 24 and thebraking force of the shoe I6 is applied to the shoe I4 through thethrust element 42.

As the linings of the shoes I4 or I6 wear, the respective stopengagingplungers 64 or 66 contact the drum I8 when the brake is appliedand are forced inwardly to a new position where they are held by thelocldng rollers 82. when the brake is released. the plungers 64 or 66engage the respective stop pins 66 or 68 and hold the shoes in a newexpanded position but with exactly the same clearance from the drum aspreviously set. This causes a further separation of the shoe endsbetween which the thrust member 42 is positioned and permits the torsionspring to expand said thrust member in accordance with the new shoeposition.

From the above it will readily appear that no adjustment takes placeuntil actual wear occurs, and that each shoe is maintained with theexact normal clearance originally set.

In the modification of Figure 3, in which corresponding parts havecorresponding reference numerals plus one hundred, the stop engagingmember is in the form of a lever I66 pivoted on the web II8 of the shoeII6 by means of a pin I18. A projection of the lever extends through theopening "4 in the rim I20 and lining I22 of the shoe and terminatesflush with the lining. The lever is provided with an arcuate edge I80centered on the center of the pivot I10, and this edge is engaged by aone-way locking cam I 82 pivoted on the shoe 6 by means of a pin 88 andurged into locking engagement with said arcuate edge by means of aspiral spring I84. The one-way locking cam is formed to permit freeinward swinging of the lever I66 and to prevent outward swingingthereof.

The operation of the brake employing this stop engaging member isidentical with that just described, and it is therefore believedunnecessary to describe it further.

' While two embodiments of my invention have been described in detail,it is not my intention to be limited to those embodiments or otherwisethan by the terms of the accompanying claims.

I claim:

1. A brake comprising a rotatable drum, a fixed support, a pair ofgenerally semicircular shoes mounted on said support and provided with awearable friction lining adapted for frictional .engagement with saiddrum, anchorage and applying means between one pair of adjacent shoeends, spring means for moving said shoe ends into and maintaining saidshoe ends in engagement with said anchorage means when the brakes arereleased, shoe positioning means intermediate the shoe ends on which theshoes are arranged to pivot so that when the brake is released thespring means in moving the shoe ends into engagement with the anchoragemeans causes the shoes to pivot on said positioning means to spread theother pair of adjacent shoe ends, said shoe positioning means comprisingstop means secured to said support, members movably mounted on andslidable through an opening in the shoes so that one end is engageablewith the drum when the brakes are applied and the other end engages withthe stop means when the brakes are released, the first named endbeciated with the other shoe and threaded into the internally threadedmember arranged between the other pair of adjacent shoe ends andconstructed to expand, in accordance with the 40 with the drum andfurther provided with a respreading of the shoes by said spring means asthe shoes pivot about said stop means, and a spring connecting theadjacent ends of the shoes between which said articulating thrust meansacts and tensioned to draw these ends toward one another, said springacting with less force than said spring means moving said shoes intoengagement with said anchorage means so that the spring will yield andstretch to the prepon derate force of said spring means when wearadjustment occurs.

2. A brake comprising a rotatable drum, a fixed support, a pair ofgenerally semi-circularshoes mounted on said drum and provided withwearable friction lining adapted for frictional engagement with thedrum, means between one end of said shoes for applying said shoesagainst the drum, an automatically expansible connecting link betweenthe other ends of the shoes, and means controlled by the wear of thefriction lining arranged to allow automatic expansion of said connectinglink including a housing carried by each shoe, a member reciprocatinglymounted in each housing for movement toward and away from the drum andextending through the shoe for engagement with the drum, adjustable stopmeans against which each member abuts mounted on said fixed support foradjustment toward and away from the drum, each housing having a surfaceinclined to'the path of movement of the member, and wedging means ineach housing acting between the inclinedsurface and the member to holdthe latter against movement outwardly toward the drum but permittingitto move in the opposite direction toward the stop means against which itabuts.

3. A brake comprising a rotatable drum, a fixed support, a shoe providedwith a wearable friction lining adapted for frictional engagementinforcing web on the side opposite to the friction lining, a memberslidably disposed along one side of said web and projecting through ahole in the shoe and the friction lining for contact with the drum, astop element carried by said fixed support against which said memberabuts in brake released position, a housing fixed on the web forming incombination therewith a guide for slidably supporting said member in apathsubstantially perpendicular to the adjacent surface of the drum, oneside of said housing extending at an angle to the pathof movement ofsaid member, a wedging element in the housing movable along the-angularside of the housing and yieldingly pressed into engagement with themember in such a way that the member is held against movement on theshoe toward the drum but is permitted movement on the shoe away from thedrum.

4. A brake comprising a rotatable drum, a fixed support, a shoe providedwith a wearable friction lining adapted for frictional engagement withthe drum and further provided with a reinforcing web on the side of theshoe opposite to the friction lining, a member pivotally supported onsaid web and projecting through a hole in the shoe and the frictionlining for contact with the drum,

-a stop element carried by said fixed support against which said memberabuts in brake released position, said member provided with an arcuateedge having its center on the pivotal point of the member, and a camelement rotatably supported on said web and bearing against the arcuateedge of the member, and spring means yieldingly 'acting to rotate saidcam element into tighter engagement with said arcuate edge, said camelement so mounted with respect to the member that it will hold thelatter against movement on the shoe toward the drum but permit movementthereof away from the drum.

WILLIAM J. RYAN.

